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Boating in the Florida keys now, 21' powerboat, and I need a navigation device that can warn me if I head towards the shallows...before I get there on the plane. Features like Selectable Depth Coloring / Multiple Depth Range Shading might help, especially if I can make 4' 3' 2' contours different shades of RED. Red cross-hatching of shallows might be ok. Alarms would be really good if they warned me I was HEADED for shallows. In a big bay with 5' depths, I need to know I've got 2' waters ahead. Hand-held MFD is out, tablets are out, anything over 7 inches won't fit. Live charting might be handy. I don't fish, just want to spend as little as possible without running aground. Thank you VERY much for any tips or sites I should check out.
Hi Mike, I see depth highlighting features like you mention on numerous brands and models of MFDs these days, though what's possible is often contingent on the specific chart card format being used. However, there is a big difference between chart presentation and chart accuracy, and I doubt that the depth data in the shallow parts of the Keys is accurate enough that you can rely on it to safely plane along with only a foot or two margin. If you see other boats doing that, the chances are good the skippers already know the area well, perhaps have marks that keep them safe and/or have learned to see the dangerous shallows well.
I agree completely, so I think I'm limited to the MFDs that let you Quickdraw Contours / SonarChart Live, etc. In other words, DIY. I'm leaning towards the Garmin 742 or the Simrad GO7, and G2 HD maps.